Kristen Bell, Dax Shepard Used Craiglist to Find Nude Hit and Run Extras

"We actually enjoy spending time together," Bell, 32, said on TODAY August 22. "Our shooting schedules take us to different cities and they separate us for 15 hours a day. When he shoots Parenthood [for NBC], I shoot House of Lies [for Showtime], so to have an excuse to shoot together and work together was a real treat."

Shepard, 37, wrote the comedy, which he also co-directed with David Palmer. With Bell's assistance, the two enlisted the help of A-list pals Bradley Cooper, 37, Kristin Chenoweth, 44, Tom Arnold, 53, Joy Bryant, 35, Michael Rosenbaum, 40, and Ryan Hansen, 31.

"Dax wrote this in six weeks. We just called all of our friends and said, 'Anybody have a couple days this summer?'" Bell explained. "Who else would we put in? They were our first choices."

When the time came to hire extras -- including a group of nude elders -- Shepard used a different method. "We did find them on Craigslist," Bell told co-hosts Hoda Kotb, 48, and Kathie Lee Gifford, 59. "That's not a joke."

The extras appear on-camera twice: first, when Bell and Shepard's characters mistakenly enter the wrong hotel room, and again when a trio of gang members makes the same unfortunate mistake.

"Everybody knew what was happening, but I'm gonna be honest: You can't really prepare for a scene like that. And Dax didn't let anybody see anything before we actually shot," Bell laughed. "So when Bradley Cooper, Joy Bryant and Ryan Hansen entered, that really was the shock on their face."

Bell -- engaged to Shepard since January 2010 -- was luckily able to keep her composure on set. "They're nudists -- they didn't care! They got there, they were excited, happy to disrobe, and they just hung out," she said. "I mean, it was so life-affirming! They were casual. Like I'm going to make it weird? No."